The U.S. space agency NASA is facing a critical deadline to make its biggest decision in a generation: whether to go forward with plans to retire the space shuttle fleet and replace it with a new mode of space travel.

President Obama took another step Wednesday toward completing his Cabinet with the appointment of Democrat Gary Locke, the nation's first Chinese-American governor and an expert on trade issues, as Commerce secretary.

Two weeks after he stood before the nation and pledged "a new era of responsibility," President Obama confronted the biggest crisis of his young presidency Tuesday as two of his key nominees withdrew over their failure to pay their taxes.

New administrations always face a cacophony of competing demands, but few presidents have been confronted with the sort of urgent and varied pleas being made to Barack Obama, amid two wars and the worst economic crisis in generations.